The research outlined in the current Revised proposal is designed to elucidate the relation between Medial Temporal Lobe (MTL) structures and memory in epileptic individuals before and after undergoing a temporal lobectomy. A secondary goal is to determine whether the non-invasive recording of event-related potentials (ERPs) can provide an index of the integrity of the MTL structures that subserve memory. Such work has implications for the neurological and neurosurgical treatment of epilepsy. Individuals suffering from medically intractable complex partial seizures will be studied immediately before and 6 months after undergoing a unilateral temporal lobectomy. Non-surgical epileptic and neurologically normal control subjects will also be tested. Two research protocols employing scalp-recorded event-related potentials (ERPs) will be used to examine memory. In one protocol subjects will be asked to attend to a target stimulus presented in one or the other visual field, and to keep a running count of the total number of targets presented. In a second protocol, subjects will be presented with words flashed on a screen, some of which will repeat at different lags (i.e., a word might repeat 1, 6, or 16 times after it was first presented). Subjects will be told to push a button whenever they see a word a second time.